INVESTMENT SECURITIES - Schedule of Amortized Cost and Fair Value of Securities Held to Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Investment Securities Held To Maturity [Line Items]
Amortized Cost	$ 4,029	$ 3,979
Gross Unrealized Gains	9	3
Gross Unrealized Losses	(303)	(338)
Fair Value	3,735	3,644
U.S. Treasury
Investment Securities Held To Maturity [Line Items]
Amortized Cost	1	1
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	1	1
U.S. government-sponsored enterprises
Investment Securities Held To Maturity [Line Items]
Amortized Cost	29	29
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	29	29
Agency MBS
Investment Securities Held To Maturity [Line Items]
Amortized Cost	865	901
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(79)	(96)
Fair Value	787	806
Agency collateralized mortgage obligations
Investment Securities Held To Maturity [Line Items]
Amortized Cost	689	714
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(81)	(95)
Fair Value	608	619
Agency commercial MBS
Investment Securities Held To Maturity [Line Items]
Amortized Cost	1,439	1,326
Gross Unrealized Gains	8	2
Gross Unrealized Losses	(32)	(44)
Fair Value	1,415	1,284
States of the U.S. and political subdivisions (municipals)
Investment Securities Held To Maturity [Line Items]
Amortized Cost	989	992
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(110)	(103)
Fair Value	879	889
Other debt securities
Investment Securities Held To Maturity [Line Items]
Amortized Cost	17	16
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Fair Value	$ 16	$ 16

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Amount excluding accrued interest, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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